J. Nannoplankton Res. 28 (1), 2006, pp .35-55 © 2006 lnternatwnal Nannoplankton Association
ISSN 1210-8049 Printed by Cambridge University Press, UK

Didemnid ascidian spicules from the Arabian Peninsula
0. Varol
Varol Research , 12 Tan-y-Bryn Road , Rhos-on-Sea, North Wales, LL28 4AE, UK; osman@varol.com
Manuscript received 9th December, 2005 ; revised manuscript accepted 24th January, 2006

Abstract In this study, 15 new didemnid ascidian genera are described: Acinodidemnum, Bactrolithus,
Bicephalodidemnum, Cephalodidemnum, Didemnobijugatus, Didemnotribaculus, Diplinthos, Disechinatus ,Geminitrabilis, Hercolithus, Ommalithus, Othniodidemnum, Paleodidemnum, Unabaculus and Velasquezia . Also
described are 42 new didemnid ascidian species: Acinodidemnum arcuatus, A . ecpalesis, A. lineola, Bactrolithus delicatus, Bicephalodidemnum amphicarenon, Cephalodidemnum carenon, C. pseudocarenon, Didemnobijugatus
dichotomus , D. zigzag, Didemnoides radiatus, Didemnotribaculus anceps, Diplinthos qatifensis, Disechinatus baculus, D . bicaudatus, D. carinatus, D . clausus, D . mediageminus, D. selenion, Fusellinus brevis, F. elongatus, F.
gigas, Geminitrabalis depressus, G. scarabaeous, Hercolithus amplexus, H. cricotus, H. petalus, Ommalithus clarus, Othniodidemnum arabianicus, Paleodidemnum acutus, P. alatus, P. caudatus, P. causianus, P. coniger, P. curvus,
P. galbulus, P. marjanensis, P. metaxy, P. phossonion, P. procerus P. pseudoacutus, P. saudicus and Unabaculus
pseudobscurus. Two new combinations, Velasquezia minuta and V. praegothica , are introduced. One new coccolith
species , Cyclagelosphaera riyadhensis , is described.
Keywords Jurassic , Early Cretaceous, didemnid ascidian spicules, taxonomy

1. Introduction
Didemnid ascidians are soft-bodied animals, with the
exception of their spicules . They are all sessile and colonial. Marine waters rich in carbonate, particularly coral
reef environments, are especially favourable for thedevelopment of didemnid ascidian colonies.
A review and classification of fossil didemnid ascidian spicules, from mainly Tertiary sediments, was originally presented by Varol & Houghton (1996). In addition,
several publications have reported fossil didemnid ascidian spicules, either as nannofossils or ascidian spicules(see Varol & Houghton , 1996). Bonet & BenvenisteVelasquez (1971) published the only study to date , from
Mexico, which deals with Mesozoic didemnid ascidian
spicules. Fossil didemnid ascidian spicules ofPliensbachien to Portlandian age have also been
described, as nannofossils , by Noel (1956), whilst
Valanginian forms have been reported by Perch-Nielsen(1988) and Rhaetian forms by Jafar (1983). Ascidian
spicules are not generally recorded, however, and certainly identification down to species level is very rare.
Didemnid ascidians are rarely reported by specialists
for the following reasons: (a) the size of the complete
spicules are usually larger than nannofossils , but smaller
than microfossils , and so they are commonly overlooked;(b) although constituent spicule rays usually fall into thenannofossil size-range, they are generally ignored, unlessthey are particularly abundant; (c) their stratigraphic and,to a certain extent, palaeoenvironmental val11e has yet to
be proved; and (d) there is possibly confusion concerning
the origin (inorganic/organic) of spicules/rays observed inassemblages.
Living didemnid ascidians display their greatest abundances in the shallow depths of the warm seas of theworld, within reefs and embayments . The fossil material
tends to reflect a similar palaeoenvironmental distribution; benthic foraminifera from sediments that containabundant ascidians are typically those that indicate shallow-marine depositional settings . Furthermore, it isnotable that nannofossil abundance is reduced when theabundance of didemnid ascidians increases, suggesting
shallowing waters.

2. Material and methods
The species described in this study are mainly derived
from core samples from exploration and development
wells drilled by Saudi Aramco in onshore and offshore
eastern Saudi Arabia (the Gawar, Qatif, Berri and Marjan
Fields). The Wadi Laban well, and the outcrop sections
Diplomat, Hanifa and Hisyan , are situated on the RiyadhMecca highway in central Saudi Arabia. Over 1000 coreand outcrop samples were taken from selected carbonate
formations of Callovian to Early Valanginian age , in orderto subdivide the reservoir intervals using assemblage
characteristics based on didemnid ascidian spicules. The
formations sampled are , in stratigraphical order, theHisyan Member of the Dhruma Formation, and the
Hanifa, Jubaila , Arab D , Sulaiy and Yamama Formations .
These mainly limestone samples, taken at a vertical spacing of between 2 and 5 feet , were prepared using the standard smear-slide technique (e .g . Bown & Young, 1998).
Detailed abundance counts of nannofossils and ascidian
spicules, using over lOO fields of view, were made foreach sample at xlOOO magnification (Figure l) .
The samples and slides, including holotypes , arestored in the Saudi Aramco offices in Dhahran, Saudi
Arabia. All the images are digital and stored in the computers of Varol Research, North Wales , UK.

Varol36~

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OxfordianCallovianc5s·

Berriasian

Kimmeridgian Tithonian

Age

Chronostratigraphy

Formation

Lithostratigraphy

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Conusphaera mexicana mexicana-·_ _,____---------~

Conusphaera mexicana minor
Nannoconus spp.
Nannoconus steinmannii minor
Nannoconus steinmannii steinmannii
Stephanolithion bigotii
St~anolithion hexum
Crepidolithus crassus
Cyclagelosphaera argoensis
Cyclagelosphaera argoensis (large)
Cyclagelosphaera deflandrei
Cyclagelosphaera margerelii
Cyclagelosphaera riyadhensis
Diazomatolithus subbeticus
Lotharingius crucicentralis
Lotharingius spp.
Retecapsa crenulata
Watznaueria barnesiae

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Watznaueria britannica
Watznaueria britannica (> 12~m )Watznaueria fossacincta
Watznaueria manivitiae

Acinodidemnum arcuatus
Acinodidemnum ecpalesis
Acinodidemnum lineola
Bactrolithus de/icatus
Bicephalodidemnum amphicarenon
Cephalodidemnum carenon
Cephalodidemnum pseudocarenon
Didemnobijugatus dichotomus
Didemnobijugatus zigzag
Didemnoides radia tus
Didemnoides rosetta- - - - + - - - - -+ Didemnotribaculus anceps
Diplinthos qatifensis- - - --;--- - - ---7- Disechinatus baculus- - - -+-- - - -+ Disechinatus bicaudatus- - - - - - - - - - Disechinatus carinatus- - - --;--------7- Disechinatus clausus- - - -+-- - - -+ Disechinatus mediageminus
Disechinatus selenion- - - - - ; - - - - - - - - 7 - Fusellinus brevis- - - -+-- - - -+ Fusellinus elongatus- - - - - ' - - - - - - - Fusel/inus gigas- - - --;--------7- Fusellinus insolitus
Geminitrabalis depressus
Geminitrabalis scarabaeus
Hercolithus amplexus
Hercolithus cricotus
Hercolithus petalus
Ommalithus clarus
Othniodidemnum arabianicus
Paleodidemnum acutus- - - --;--------7- Paleodidemnum alatus- - - -+-- - - -+ Paleodidemnum caudatus
Paleodidemnum causianus
Paleodidemnum coniger
Paleodidemnum curvus
Paleodidemnum galbulus
Paleodidemnum marjanensis

Paleodidemnum metaxy
Paleodidemnum phossonion
Paleodidemnum procerus
Paleodidemnum pseudoacutus
Paleodidemnum saudicus
Unabaculus pseudobscurus
Velasquezia minuta
Velasquezia praegothica

Figure 1: Nannolith , coccolith and didemnid ascidian spicule stratigraphical ranges , Arabian Peninsula

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"iii'a:""'Didemnid ascidian spicules .. .Arabian Peninsula

3. Biostratigraphy
So far, little research has been carried out on fossil didemnid ascidian spicules and , consequently, the stratigraphic
ranges of individual species cannot yet be determined precisely, and so their biostratigraphic potential is limited.
Further research into this group of fossils is also requiredin order to realise their sequence stratigraphical interpretation potential. Despite this , the first application of combined ascidian and foraminiferal stratigraphy to Jurassic
Saudi Arabian sediments was carried out by Hughes et al.
(2004), whilst Hughes (2004) presented a summary of theages and palaeoenvironments of the Middle and Late
Jurassic formations of Saudi Arabia, also using didemnid
ascidians.
The highest stratigraphicaloccurrence ofDidemnoides rosetta was found in the upper part of the
Arab D Formation. At this level , nannofossils are sparse,
but the sporadic occurrence of Watznaueria barnesiae
was noted. The Arab D Formation has been dated as
Kimmeridgian, mostly on ammonoid evidence (Enay,
1987; Sharland et al., 2001; Hughes, 2004).
The highest occurrence of Cyclagelosphaera riyadhensis sp. nov. was recorded at the top of the Jubaila
Formation, together with rare to frequent nannofossils ,including Watznaueria britannica, W. barnesiae andCyclagelosphaera margerelii . In the lower part of theJubaila Formation, the highest occurrences of
Cyclagelosphaera dejlandrei and Didemnoides radiatus
sp. nov. were determined. The Jubaila Formation is dated
as Kimmeridgian on ammonoid and benthic foraminiferal
evidence (Sharland et al., 2001; Hughes, 2004). An Early
Tithonian age , from palynological evidence (Clarke,
1988), is not considered to be valid .
The highest occurrence of Watznaueria manivitiae
was recorded in the Hanifa Formation, together with anincreased abundance and diversity of nannofossils,
including Crepidolithus crass us. Manivit (1987) also
recorded the highest occurrence of W. manivitiae within
the Hanifa Formation , assigning it to the Early Oxfordian.
W. manivitiae has been recorded from stratigraphicallyhigher elsewhere (e.g. Bown , 1998), but in the study area
was not recorded above the Oxfordian . An influx of W.
britannica was recorded within the Hanifa Formation,
together with the highest occurrences of Stephanolithion
bigotii and Lotharingius crucicentralis. Ammonoid andforaminiferal evidence provide an Early to Late
Oxfordian age for the Hanifa Formation (Enay, 1987;
Hughes, 2004).
The oldest sediments studied herein are from theHisyan Member of the Upper Dhruma Formation.
Occurrences of Stephanolithion hexum and S. bigotii,
together with C. deflandrei and abundant W. britannica,
indicate a Bathonian age. The abundant occurrence of W.
britannica was also recorded from the Hisyan Member
by Manivit (1987), who assigned it to the basal Callovian
to uppermost Bathonian. Ammonoid evidence is absent
from the Hisyan Formation, but brachiopod evidence

37(Cooper, 1987) suggests a Callovian age.
The dominant feature of these data is the high abundance (up to 100% of the assemblages) of didemnid ascidian spicules throughout the well sections. The relative
abundances and diversity of the didemnid ascidian
spicules have been quantified to allow recognition of correlative events. The association of these correlative
events, along with nannofossil and micropalaeontologicalevidence, provides a robust framework for the correlationof the wells across the region. The correlative value of thequantitative didemnid ascidian spicule events has also
been tested using wireline log evidence, where no otherfossil groups were recorded . The results were consistent.
Nannofossil recovery in the samples varies greatly
but, in general , poorly-preserved and low-diversity
assemblages were obtained. This is considered to be theresult of the shallow-water setting. Nannofossil abundance increased as the depositional setting deepened , asindicated by benthic foraminifera. The highest stratigraphical occurrences of nannofossils were recorded atflooding surfaces. Only at these levels did diversity andpreservation of nannofossils improve. W. barnesiae, C.
margerelii and W. britannica are the most abundant nannofossils recovered.

4. Taxonomy
Below, 15 new didemnid ascidian spicule genera and 42
new species are described , along with one new coccolith
species. Two new didemnid ascidian combinations arealso introduced .

4.1. Didemnid ascidian spicules
The arrangement and shape of the spicule rays, presenceor absence of appendices, and number and position of
appendices are utilised as diagnostic features for the identification of didemnid ascidians (Figure 2). The adoptionof ray morphology as a system of classification enables
the scientist to identify individual species, even if onlyisolated rays are preserved.
The fossil forms described below are classified as
didemnid ascidian spicules for the following reasons:
Bonet & Benveniste-Velasquez (1971) have already published some of the species cited in this study, including
Fusellinus insolitus (as Ascidites dubius), Velasquezia
minuta comb. nov. (as Didemnoides minutum),
Velasquezia praegothica comb . nov. (as Didemnoides
minutum) and Didemnoides rosetta. Furthermore, Noel
(1956) presented a scanning electron micrograph and aline-drawing of Fusellinus insolitus , from Jurassic sediments, displaying its fibrous structure. This evidence confirms the link between the well-known Micrascidites vulgaris Deflandre & Deflandre-Rigaud , 1956 and the newly
described forms.
Another common feature between the well-known
ascidians and the forms described here is that the spiculerays display a blue colour (when aligned in a NW-SE
direction) in cross-polarised light (XPL) with a gypsum

38

Varol

plate. Photographic evidence for a fibrous structure tothese forms has been observed in well-preserved samples
from Trinidad, but as these are from confidential wells ,they are currently unavailable for publication . Withinthese samples is evidence that indicates that Fusellinus
brevis sp . nov. forms a spherical spicule.
In the author 's experience, inorganic objects typicallydisplay sharp edges and simple structures, whilst theforms described here display complex morphologies, witha fibrous structure in well-preserved material. The taxa
used in this publication have been applied , by M. Girgis(pers . comm., 2005), in West Africa and found to be ofstratigraphic utility.
Most of the species described herein have long stratigraphical ranges . It has been observed , however, thatspecies of Didemnoides are not found above theKimmeridgian , and that species of Didemnobijugatus
gen . nov. and Hercolithus gen. nov. have not been foundabove the Berriasian.lt is anticipated that future work will
permit further stratigraphical subdivision and, thus,
potentially increase their biostratigraphic application. It is
recommended that the geochemical composition of
spicules should be examined, for the purpose of further
confirming their origin and taxonomic affinity.
The terminology used in this study is presented in
Figure 2. The following four types of spicule have been
identified: (a) fusiform type - spicules made up of a single , or several, rays, with or without appendices , as inVelasquezia gen. nov. and Paleodidemnum gen. nov.; (b)petaloid type - brick-like rays forming a petal-like circular or elliptical wall , as in Hercolithus gen. nov.; (c)spherical type - spicules composed of rays radiatingfrom the centre of the spicule, and characteristic ofFusellinus; and (d) asteroid type - star-shaped spicules
made up of numerous rays, and peculiar to Didemnoides .
Sketches of the ascidian taxa are shown in Figure 3.
Acinodidemnum gen. nov.
Type species: Acinodidemnum lineola sp . nov.
Derivation of name: From acino, Latin for 'thorn' , or'appendix ' , referring to its appendices. Diagnosis:
Didemnid ascidian spicules having a fusiform, or modified fusiform, ray with single bilateral appendices.
Description: The rays are fusiform in shape, but may be
curved. The spicule has two appendices, one on each sideof the ray. These appendices are believed to help join
spicules to each other. The species of this genus are distinguished by the position of the appendices and the shapeof the ray. Remarks: Acinodidemnum is distinguishedfrom Didemnotribaculus gen. nov. by having a single
appendix on each side of the ray. The latter has two
appendices on one side and a single appendix on the otherside of the ray.
Acinodidemnum arcuatus sp. nov.
Pl.l, figs 26-28. Derivation of name: From arcus, Latinfor 'bow-like', referring to the concave sides of the ray.

Diagnosis: Spicule with a bow-like ray, having a short
appendix on one side and a large appendix on the otherside. Remarks: The ray is modified fusiform. It appears
bow-like due to the different sizes of the depressions at
the bases of the appendices on the ray. There are different
sizes of single appendices on each side of the ray. The
small appendix may or may not be central. The base of thelarge appendix extends almost along the entire side of theray. A . arcuatus is distinguished from other species ofAcinodidemnum by having a bow-shaped ray and two distinctly different sizes of appendix. Holotype: Pl.l, figs
26,27 (same specimen). Dimensions ofholotype: Lengthof ray= 6.0Jlm; maximum width of ray= 3.0Jlm ; lengthof appendix = 4.5Jlm, maximum width of appendix =3.5Jlm. Type level: Sulaiy Formation (Berriasian). Type
locality: Well MRJN-39, 7981.20' (core), Marjan Field,
offshore eastern Saudi Arabia . Occurrence: Upper
J urassic-Valanginian.
Acinodidemnum ecpalesis sp. nov.
Pl.1 , figs 20 , 25, 30. Derivation of name: From ecpalesis, Greek for 'dislocation' , referring to the misalignmentof the appendices. Diagnosis: A species ofAcinodidemnum in which the appendices are offset along
the ray. Remarks: The ray is fusiform but usually strongly curved. Appendices are short and offset along the ray.
A. ecpalesis differs from A. lineola sp. nov. by having
these dislocated/offset appendices . In the latter, theappendices are aligned. Moreover, the ray in A. ecpalesis
is usually curved, whereas in A. lineola sp. nov. the ray isalways plain fusiform. Holotype: Pl.l, figs 25 , 30 (samespecimen). Dimensions of holotype: Length of ray =6 .5Jlm; maximum width of ray = 3.0Jlm. Type level:
Sulaiy Formation (Berriasian). Type locality: Well
LWHH-17 , 8656 .20' (core), Marjan Field, offshore eastern Saudi Arabia. Occurrence: Upper JurassicPleistocene .
Acinodidemnum lineola sp . nov.
Pl.l, figs 16-19.
1971 Didemnoides minutum Bonet & BenvenisteVelasquez, pp.ll-13, pl.l, figs 4, 19; non pl.l , figs
1-3,5-18.
2002 Uniplanarius sp. Herrle, p.78, p1.6, fig.24 .
Derivation of name: From lineola, Latin for 'aligned' ,referring to the alignment of the appendices. Diagnosis: A
species of Acinodidemnum in which the appendices arealigned. Remarks: The ray is always fusiform. The short
appendices are situated in a median or submedian location , but are always aligned. This species is distinguishedfrom A. ecpalesis in having aligned appendices. It differsfrom A . arcuatus in having almost equal-sized appendices. In A . arcuatus, one of the appendices is large andthe spicule ray is bow-tie-shaped . Holotype: Pl.l , fig.l6.
Dimensions of holotype: Length of ray= 14.5Jim; maximum width of ray = 5.5Jlm. Type level: Arab D
Formation (Kimmeridgian). Type locality: Well Qatif-48,

Didemnid ascidian spicules ... Arabian Peninsula

39

DIDEMNID ASCIDIAN SPICULE TERMINOLOGY

fusiformray( t ( double )singlebilateral
appendicesunipolarappendixunilateralappendices. \b1polarappendices\ duplextrays

polar appendix
1
truncated end
unilateral appendix

singleI

angular appendix

double

I ~

t

/

,..

~

\ t

fusiform ray•vvrx

truncated
fusiform rayt t

modifiedfusiform raytt

rectangularraysjoined part of ray

petaloid
spicule~free part of ray/ ray ~
suturet\central process

delicate part
depression
ridge/
asteroid spicule
Figure 2: Didemnid ascidian spicule terminology and identifying features

Varol40

F. brevis

A. lineola
A. ecpalesis

F. insolitus

A. arcuatus

F. elongatus

Acinodidemnum

Fusellinus
D. anceps

V minuta

DidemnotribaculusA

V praegothica

VelasqueziacB

G. scarabeous
P. alatus
P. saudicus

D.qatifensis
G. depressus

P. causianus

Diplinthos

Geminitrabalis
P. caudatus

P. pseudoacutus
P. metaxy
P. phossonion
P. acutus

D. clausus

D. baculus

P.galbulus
P. coniger
P. curvus
P.procerus

D. mediageminus

Paleodidemnum

P. marjanensis

D. selenion

D. bicaudatus

D. carinatus

Disechinatus

C. riyadhensis
D. amphicarenon

Bicephalodidemnum
D. radiatus

Cyclagelosphaera
U pseudobscurus

Unabaculus

Didemnoides

D. rosetta
H. cricotus

C. carenon

C. pseudocarenon

Cephalodidemnum

D. dichotomos

H. amplexus

B. delicatus

H. p etalus

0. arabianicus

D. zigzag

Didemnobijugatus

Bactrolithus

Othniodidemnum

Hercolithus
0. clarus

0
Ommalithus

Figure 3: Sketches of the didemnid ascidian spicules, and the coccolith Cyclagelosphaera, described herein , highlighting differentiation between the taxa

Didemnid ascidian spicules .. .Arabian Peninsula

7946 .00 ' (core), Qatif Field , eastern Saudi Arabia.
Occurrence: Upper Jurassic-Pleistocene.
Bactrolithus gen. nov.
Type species: Bactrolithus delicatus sp. nov. Derivationof name: From bactro, Greek for 'rod', or 'stick ', referring to its shape. Diagnosis: Didemnid ascidian spicule
having fusiform rays without appendices. The rays arecompressed in the middle, where two rays join each otherto form a complete spicule . Remarks: The angle between
the two rays varies but is never at a right-angle. The raysof Bactrolithus are distinguished from the rays of
Fusellinus by having a thinned part in the middle of theray.
Bactrolithus delicatus sp. nov.
PIA, figs 1-4. Derivation of name: From delicatus,
Greek for 'delicate', referring to the delicate middle partof the ray. Diagnosis: The spicule ray is fusiform andthinned in the middle, where two rays are joined to form
an asymmetric cross . Remarks: The complete spicule isformed by two rays which are fusiform in shape. The rays
are joined to each other at their thinned parts. The opposite angles between the rays are usually equal. No appendices are present. The rays of B. delicatus are distinguished from the rays of Fusellinus by being compressedin the middle. In B. delicatus, each ray is joined by its
thinned part to form a complete spicule that is an asymmetrical cross, whereas in Fusellinus the rays join eachother to form a spherical spicule. Holotype: PlA , fig.l.
Dimensions of holotype: Length of ray = 17 .5pm; maximum width of ray = 7 .5pm; length of thinned part =7 .5pm. Type level: Arab D Formation (Kimmeridgian).
Type locality: Well Qatif-48 , 7496.00' (core), Qatif Field,
eastern Saudi Arabia. Occurrence: Upper Jurassic-Lower
Valanginian.
Bicephalodidemnum gen. nov.
Type species: Bicephalodidemnum amphicarenon sp.
nov. Derivation of name: From bi, Latin for 'two', andcephalo, Greek for ' head ', referring to its head-likeappendices at each pole of the ray. Diagnosis: Didemnid
ascidian spicule having a ray with an appendix at eachpole. Remarks: The ray, together with appendices, isfusiform in shape. The sutures between the appendicesand the ray are zigzag-shaped. Bicephalodidemnum is distinguished from Cephalodidemnum gen. nov. by having
an appendix at each pole of the ray. Cephalodidemnum
has a single appendix at one pole of the ray.
Bicephalodidemnum differs from Disechinatus gen. nov.
in the position of the appendices. The appendices arebipolar in Bicephalodidemnum, whereas appendices areunilateral in Disechinatus.
Bicephalodidemnum amphicarenon sp. nov.
PlA, figs 15 , 16. Derivation of name: From amphi ,Greek for 'on both sides', and careno, Greek for ' head ',41

referring to its cap-like appendices at the poles of the ray.
Diagnosis: Species of Bicephalodidemnum having caplike appendices at both poles of the ray. Remarks:
Zigzag sutures separate the appendices from the ray. B.
amphicarenon is distinguished from Cephalodidemnum
carenon gen. et sp. nov. by having bipolar appendices ,whereas the latter has a monopolar appendix. The speciesof Disechinatus gen. nov. are distinguished from B.
amphicarenon in having two unilateral appendices.
Holotype: PlA, figs 15, 16 (same specimen). Dimensionsof holotype: Length of ray with appendices = 7 .5pm;
maximum width= 4.5pm. Type level: Sulaiy Formation(Berriasian) . Type locality: Well Marjan-39 , 8372 .70'
(core), Marjan Field, offshore eastern Saudi Arabia.
Occurrence: Berriasian-Lower Valanginian.
Cephalodidemnum gen. nov.
Type species: Cephalodidemnum carenon sp. nov.
Derivation of name: From cephalo, Greek for 'head',referring to its head-like appendix. Diagnosis: Didemnid
ascidian spicule having a fusiform ray with an appendix at
one pole. Remarks: The ray with appendix is fusiform inshape. Cephalodidemnum is distinguished from
Paleodidemnum gen. nov. by having a polar appendix,
whereas in the latter the appendix is unilateral.
Cephalodidemnum carenon sp . nov.
PlA, figs 17, 18. Derivation of name: From careno,
Greek for 'head ', referring to its single , head-like appendix. Diagnosis: Spicule having a fusiform ray with anappendix at one of the poles. The suture between the ray
and the appendix is zigzag-shaped. Remarks: The appendix looks like a cap situated at one of the poles of the ray.
A zigzag suture joins the ray to the appendix , whichappears as a continuation of the ray. C. carenon is distinguished from C. pseudocarenon sp. nov. by the shape of
the appendix. The appendix is cap-like and joins the
spicule ray with a zigzag suture in C. carenon, whereas inC. pseudocarenon , the small appendix is partially inserted into to the depression at one pole of the ray. Holotype:
PlA , figs 17, 18. (same specimen). Dimensions of holotype: Length of ray and appendix= 8.5pm; length of ray= 5.5pm; maximum width = 5.0pm. Type level: Su1aiyFormation (Berriasian). Type locality: Well Marjan-39 ,8269.20' (core), Marjan Field, offshore eastern Saudi
Arabia. Occurrence: Lower Valanginian-Berriasian.
Cephalodidemnum pseudocarenon sp. nov.
PIA , figs 12-14, 19. Derivation of name: From pseudo,
Greek for 'false', referring to its false similarity to C.
carenon. Diagnosis: Species of Cephalodidemnum with asmall appendix, partially inserted into a depression at onepole of the ray. Remarks: C. pseudocarenon is distinguished from Paleodidemnum caudatus gen. et sp. nov. in
the position of the appendix. The appendix is located at
one pole of the ray in C. pseudocarenon, whereas theappendix is unilateral, but in an angular position , in P.

42

Varol

caudatus. Holotype: Pl.4, figs 14, 19 (same specimen).
Dimensions of holotype: Length of ray = 5.0Jlm ; maximum width of ray= 5.0Jlm. Type level: Sulaiy Formation(Berriasian). Type locality: Well Marjan-64 , 8225.20'(core), Marjan Field, offshore eastern Saudi Arabia.
Occurrence: Lower Valanginian-Berriasian.
Didemnobijugatus gen. nov.
Type species: Didemnobijugatus dichotomus sp. nov.
Derivation of name: From jugum, Latin for 'yoked
together ', or 'double', referring to the double rays .
Diagnosis: Didemnid ascidian spicule made up of two
rays without an appendix . Remarks: The spicule is a
modified semicircular or modified fusiform form. The
rays are joined along their lengths on their relatively flatter sides. Each ray in the spicule is not identical. The
suture between the spicule rays is straight or zigzagged.
Didemnobijugatus dichotomus sp. nov.
Pl.4, figs 30-33. Derivation of name: From dicho , Greek
for 'two', and tomos , Greek for ' part' , referring to thetwo rays. Diagnosis: Spicule having two semicircularrays joined along their relatively flat sides. The suture
between the rays is straight, or slightly kinked in the middle. Remarks: One of the rays is usually slightly larger
and has a shallow depression at its periphery. D. dichotomus is distinguished from D. zigzag sp. nov. by having analmost straight suture between the rays and a shallow
depression on one of the rays. Holotype: Pl.4, figs 30, 31(same specimen). Dimensions of holotype: Length =6 .5Jlm ; width = 6 .0Jlm. Type level: Sulaiy Formation(Berriasian). Type locality: Well LWHH-17, 8683.20'(core), Marjan Field, offshore eastern Saudi Arabia.
Occurrence: Upper Jurassic-Lower Valanginian.
Didemnobijugatus zigzag sp. nov.
Pl.4, figs 27, 28. Derivation of name: From zigzag, Latinfor 'alternately changing direction by sharp angles' , referring to the suture between the spicule rays. Diagnosis:
Spicule having two modified fusiform spicules joined
along their relatively flat sides. The suture between therays is zigzagged. Remarks: This species is distinguishedfrom D. dichotomus by having a zigzag suture between
the rays . Moreover, in D . zigzag, the rays are modified
fusiform in shape and lack a peripheral depression .
Holotype: Pl.4, figs 27, 28 (same specimen). Dimensionsof holotype: Length= 7 .OJlm; width= 6.5Jlm. Type level:
Sulaiy Formation (Berriasian). Type locality: Well
MRJN-64, 8511.20' (core), Marjan Field, offshore eastern
Occurrence:
Berriasian-Lower
Saudi
Arabia.
Valanginian.
Didemnoides Bonet & Benveniste-Velasquez, 1971
Type species: Didemnoides rosetta Bonet & BenvenisteVelasquez, 1971. Remarks: Asteroid didemnid ascidian
spicule made up of 10 to 24 rays . The tips of the rays areusually triangular. The species of this genus are distin-

guished by the width of their rays.
Didemnoides radiatus sp. nov.
Pl.3 , figs 31, 32. Derivation of name: From radiatus,
Latin for 'rayed', referring to its multiple rays . Diagnosis:
Species of Didemnoides having 10 to 24 slender rays. The
maximum width of the rays is <2.5Jlm. Remarks: The
spicule appears brownish-blue under XPL. The tips of therays are triangular. This form is distinguished from D.
rosetta by having narrower rays (<2 .5Jlm). Holotype:
Pl.3 , fig .31. Dimensions of holotype: Diameter =16.0Jlm . Type level: Jubaila Formation (Kimmeridgian).
Type locality: Wadi Laban Well , Sample 40', RiyadhMecca highway, central Saudi Arabia . Occurrence:
Upper Jurassic. The last occurrence of this form wasnoted in the upper part of the Jubaila Formation.
Didemnoides rosetta Bonet & Benveniste-Velasquez,
1971
Pl.3, figs 33, 34 .
1971 Didemnoides rosetta Bonet & BenvenisteVelasquez, pp.10-ll , p1.2 , figs 1-6; p1.3 , figs 1-6.
Remarks: The maximum width of the rays is always>2.5Jlm . The tips of the spicule rays are triangular. D.
rosetta is distinguished from D. radiatus by having wider
rays. Occurrence: Upper Jurassic . The last occurrence ofD. rosetta was noted in the upper part of the Arab D
Formation.
Didemnotribaculus gen. nov.
Type species : Didemnotribaculus anceps sp. nov.
Derivation of name: From tri, Latin for ' three', and baculum, Latin for 'rod', referring to the number of its appendices. Diagnosis: Didemnid ascidian spicule having afusiform ray with three bilateral appendices , two on one
side and one on the other. Remarks: The position of theappendices on each side of the ray can vary, but always
there are two on one side and one on the other.
Didemnotribaculus differs from Acinodidemnum in having three bilateral appendices , whereas the latter has only
two .
Didemnotribaculus anceps sp. nov.
Pl .l , figs 8-10. Derivation of name: From anceps , Latinfor 'two-sided', referring to the appendices on both sidesof the ray. Diagnosis: Spicule having a fusiform ray with
two appendices on one side and a single appendix on theother side. The position of the appendices varies.
Remarks: The appendices may be confined to the middle
part of the ray, or to one of the poles of the ray. Holotype:Pl.l, fig .9. Dimensions of holotype: Length = ll.5Jlm;
maximum width = 3 .5Jlm . Type level: Arab D Formation(Kimmeridgian). Type locality: Well HRDH-87,
7074.10 ' (core), Ghawar Field, eastern Saudi Arabia.
Occurrence: Upper Jurassic-Lower Valanginian .

Didemnid ascidian spicules .•.Arabian Peninsula

Diplinthos gen. nov.
Type species: Diplinthos qatifensis sp. nov. Derivation of
name: From dis , Greek for 'double', and plinthos, Greek
for ' brick' , referring to its two brick-like rays. Diagnosis:
Spicule made up of two subrectangular rays and one
appendix. Remarks: The rectangular rays are joined
together along their short sides. A single appendix extends
from these rays. The width of the appendix base is almost
equal to the combined lengths of the two joined rays.
Diplinthos is distinguished from Geminitrabalis nov. gen.
in having two rectangular rays joined along their shortersides and without a depression. In Geminitrabalis, the two
elongated rays are joined along their length. The rays ofGeminitrabalis have depressions along the suture near thepoles, where an appendix sits.
Diplinthos qatifensis sp. nov.
Pl.3, figs 16-19. Derivation of name: From the type
locality, the Qatif Field, eastern Saudi Arabia. Diagnosis:
This spicule has two subrectangular rays joined along
their short sides. The large appendix extends from their
combined longer sides . Remarks: The rays are equal indimension in well-preserved specimens , but one of theedges is slightly angled. The large appendix extends fromthe concavity formed where the two rays are joined. The
maximum width of the appendix is slightly shorter than,or equal in length to, the joined rays. Holotype: Pl.3, figs
16, 17 (same specimen). Dimensions of holotype: Lengthof rays= 5.5Jtm; width of rays= 2 .5Jtm ; height of appendix
3.5Jtm. Type level: Arab D Formation(Kimmeridgian). Type locality: Well Qatif-40 , 7485.80'(core), Qatif Field, eastern Saudi Arabia. Occurrence:
Upper Jurassic.
Disechinatus gen nov.
Type species: Disechinatus clausus sp. nov. Derivationof name: From dis, Greek for 'double', and echinos,
Greek for 'spine', referring to its two appendices.
Diagnosis: Didemnid ascidian spicule having a ray with
two unilateral appendices. The shape of the ray varies
from fusiform to half-moon-shaped. Remarks: Twoappendices extend from one side of the ray. The species ofthis genus are distinguished by the size and position of theappendices and the shape of the ray. Disechinatus is distinguished from Paleodidemnum gen. nov. in having two
unilateral appendices , whereas the latter has only one unilateral appendix.
Disechinatus baculus sp. nov.
Pl.5, figs 16-20. Derivation of name: From baculum,
Latin for 'rod', referring to its large appendices.
Diagnosis: Species of Disechinatus having a fusiform ray
and double unilateral appendices. The combined length of
the bases of the appendices is approximately equal to thelength of the ray. The bases of the large appendices (compared to the ray) do not form a distinct depression on theray. Remarks: The appendices are usually joined to each43

other along their long sides. The ray may form a low ridge
between the appendices. This form artificially resembles
the Paleocene nannofossil species Fasciculithus pileatus.
D. baculus is distinguished from D. clausus sp. nov. by
the shape of its ray, as the ray in D. baculus is elongatedfusiform whereas the ray is rhomboidal in D. clausus.
Holotype: Pl.5 , fig.l8. Dimensions of holotype: Lengthof ray= 7.5Jtm ; width of ray= 3.5Jtm; maximum width ofappendix= 3.5Jtm; length of appendices= 5.0Jtm . Typelevel: Arab D Formation (Kimmeridgian). Type locality:
Well Qatif-46, 7441.20 '(core), Marjan Field , offshore
eastern Saudi Arabia. Occurrence: Upper Jurassic-Lower
Valanginian.
Disechinatus bicaudatus sp. nov.
Pl.5, figs 26-29. Derivation of name: From bi, Latin for'two' , and cauda , Latin for ' appendix', or 'tail', referringto the two appendices near one of the poles of the ray.
Diagnosis: Spicule having a fusiform ray with two appendices located in a depression near one of the poles. Thereis usually no gap between appendices.
Remarks: D . bicaudatus is distinguished from D . mediageminus sp. nov. by the position of the appendices. In D.
bicaudatus, the appendices are located near one pole of
the ray, whereas in D. mediageminus, the appendices are
confined to the middle of the ray. Holotype: Pl.5 , fig.26.
Dimensions of holotype: Length = 9.5Jtm; maximum
width = 5.0Jtm. Type level: Sulaiy Formation(Berriasian) . Type locality: Well MRJN-64 , 8323.20'(core), Marjan Field, offshore eastern Saudi Arabia.
Occurrence: Upper Jurassic-Lower Valanginian.
Disechinatus carinatus sp. nov.
Pl.5, figs 21-23. Derivation of name: From carina, Latinfor 'ridge', referring to the ridge formed by the ray
between the appendices. Diagnosis: Species ofDisechinatus having a truncated fusiform ray with double
unilateral appendices located in depressions on the ray.
The ray forms a distinct ridge between the appendices.
Remarks: The truncated fusiform ray resembles a shoe
shape, due to the marked depressions and the ridge to one
side. The appendices are different sizes and never toucheach other. The appendix near the truncated end is larger
and located in a more pronounced depression. Holotype:
Pl.5 , fig.21. Dimensions of holotype: Length of ray =6.0Jtm; maximum width of ray (at the ridge) = 3.5Jtm.
Type level: Arab D Formation (Kimmeridgian). Type
locality: Well Qatif-58, 8091.20' (core), QatifField , eastem Saudi Arabia. Occurrence: Upper Jurassic-Lower
Valanginian.
Disechinatus clausus sp. nov.
Pl.5 , figs 11-14. Derivation of name: From clausus ,Latin for 'closed', referring to the closed, 'V'-shaped
suture formed by the bases of the appendices where theyjoin the ray. Diagnosis: Species of Disechinatus having a
diamond-shaped fusiform ray with large (relative to ray)

44

Varol

double unilateral appendices. The bases of the appendicesform a 'V' -shaped suture where they join the ray.
Remarks : Two unilateral appendices dominate thespecies. The lengths of the appendices are almost equal totheir width. D . clausus is distinguished from D . baculusby the shape of its ray ; D. clausus has a diamond-shaped
ray, whereas D. baculus has an elongated fusiform ray.
Moreover, the suture between the ray and appendices is'V' -shaped in D. clausus, whereas it is straight in D. baculus. Holotype: Pl.5 , fig.13. Dimensions of holotype:
Length of ray= 4.5Jim; maximum width of ray= 3.0jim;
maximum length of appendix = 4.5jim ; maximum widthof appendix = 4 .5Jim. Type level: Arab D Formation(Kimmeridgian). Type locality: Well Qatif-58 , 7475.00 '(core) , Qatif Field, eastern Saudi Arabia. Occurrence:
Upper Jurassic-Lower Valanginian.
Disechinatus mediageminus sp. nov.
Pl.5 , figs 24, 25, 30. Derivation of name: From medius ,Latin for 'middle ', and geminus, Latin for 'twin', referring to the median location of appendices on the ray.
Diagnosis: Spicule having a fusiform ray with mediandouble unilateral appendices. The appendices are verysmall in comparison to the size of the ray. Remarks: D.
mediageminus is distinguished from D . bicaudatus by the
position of the appendices; these are at the middle of theray in D . mediageminus, but near to one pole of the ray in
D. bicaudatus. Holotype: Pl.5 , figs 24, 25 (same specimen). Dimensions ofholotype: Length= 7.0pm; width =2.5pm. Type level: Sulaiy Formation (Berriasian). Type
locality: Well MRJN-64 , 8600 .70 ' (core) , Marjan Field,
offshore eastern Saudi Arabia. Occurrence: Upper
J urassic-Lower Valanginian.
Disechinatus selenion sp . nov.
Pl.5 , figs 9, 10 , 15. Derivation of name: From selene,
Greek for 'small moon', referring to its half-moon-shaped
ray. Diagnosis: Species of Disechinatus having a fusiform
ray with a half-moon shape and bearing double unilateralappendices along the flat side. The appendices are usually joined to each other, and their combined bases almost
extend along the entire flat side of the ray. Remarks: The
flat side of the ray may form a slight ridge between the
appendices. D . selenion is distinguished from all otherspecies of Disechinatus by its half-moon-shaped ray.
Holotype: Pl.5 , figs 9, 10 (same specimen). Dimensionsof holotype: Length of ray = 6.0pm; maximum width of
ray = 4.0Jim. Type level: Arab D Formation(Kimmeridgian). Type locality: Well Qatif-48 , 7598.30'(core), Qatif Field, eastern Saudi Arabia. Occurrence:
Upper Jurassic.
Fusellinus Noel , 1956
Type species: Fusellinus insolitus Noel, 1965. Synonym:
Ascidites Bonet & Benveniste-Velasquez, 1971.
Remarks: Didemnid ascidian spicule composed offusiform rays without appendices. The rays are joined toeach other along their lengths to form a spherical complete spicule. The ratio between the length of the joinedpart of the rays and the free part of the rays varies. No difference in diameter is noted between the free and joinedparts of the ray.
Fusellinus brevis sp. nov.
Pl.l , figs 11-13.
1971 Didemnoides minutum Bonet & BenvenisteVelasquez, pp . lO-ll, pl.l, figs 6, 14; non pl.l, figs
1-5 , 7-13 , 15-19.
Derivation of name: From brevis, Latin for 'short', referring to its length, relative to other species of the genus.
Diagnosis: A short species of Fusellinus having afusiform ray. The length of the rays are <10Jtm. Mainly
isolated rays have been observed. Rarely, complete spherical spicules have been observed. Remarks: The rays area yellowish-brownish colour in XPL. The length of thejoined part of each ray is equal to , or greater than , the freepart of the ray. The rays of F. brevis are distinguishedfrom those of F. insolitus in being shorter, and by theircolour. Holotype: PI. I , fig.13. Dimensions of holotype:
Length of ray = 7 .Ofl. m; maximum width of ray = 4 .Op m.
Type level: Arab D Formation (Kimmeridgian). Type
locality: Well Qatif-67 , 7124.50' (core), QatifField, eastern Saudi Arabia. Occurrence: Permian-Pleistocene.
Fusellinus elongatus sp. nov.
Pl.l , figs 14, 15. Derivation of name: From elongatus ,Latin for 'elongated' , referring to the elongated shape ofthe rays . Diagnosis: A species of Fusellinus having relatively long , elongated rays. Remarks: The colour of therays is yellowish-brown in XPL. This form is distinguished from F. brevis by its elongated shape. Holotype:Pl.l, fig .15. Dimensions of holotype: Length of ray =13.5Jim; maximum width of ray = 3.0pm. Type level:
Arab D Formation (Kimmeridgian) . Type locality: Well
Qatif-58 , 7438.70' (core) , Qatif Field , eastern Saudi
Arabia. Occurrence: Upper Jurassic-Pleistocene.
Fusellinus gigas sp. nov.
Pl .l , figs l-5. Derivation of name: From gigas, Greek for'giant', referring to its relatively large size. Diagnosis: A
species of Fusellinus having relatively large fu siform
rays. The length of the rays is >20J1.m . Remarks: The
dominant colour of the rays is greenish-blue in the outerpart and reddish in the central part in XPL. The length of
the joined parts of the rays greatly varies. Holotype: Pl.l ,fig.4. Dimensions of holotype: Length of ray= 2l.O}tm;
maximum width of ray = 9.0pm. Type level: Arab D
Formation (Kimmeridgian). Type locality: Well Qatif-46 ,7409 .00' (core), Qatif Field , eastern Saudi Arabia.
Occurrence: Upper Jurassic-Lower Valanginian.
Fusellinus insolitus Noel, 1965
Pl.l, figs 6, 7.
1965 Fusellinus insolitus Noel , p.172, p1.27, figs 9, 10,Didemnid ascidian spicules .•.Arabian Peninsula

text-fig.73.
1971 Ascidites dubius Bonet & Benveniste-Velasquez ,p.lO, figs IA-10.
1971 Didemnoides minutum Bonet & BenvenisteVelasquez, p.lO, text-fig.l.
1971 Didemnoides minutum Bonet & BenvenisteVelasquez, pp.l0-11, pl.l, figs 2, 15, 16; non pl.l,figs I, 3-14, 17-19.
Remarks: Species of Fusellinus having rays > 10ytm and<20ytm in length. The dominant colour of the rays is usually greenish-blue in XPL , although, rarely, the central
part of the rays is reddish . The rays of this form resemble
those of Micrascidites vulgaris Deflandre & DeflandreRigaud (1956) , but differ from it by having smooth surfaces, whereas the latter has fibrous surfaces. The rays
form a stellate spicule in M. vulgaris, whereas they are
believed to form spherical spicules in F. insolitus.
Occurrence: Permian-Pleistocene.

Geminitrabalis gen nov.
Type species: Geminitrabalis depressus sp. nov.
Derivation of name: From geminus, Latin for ' twin' , andtrabalis, Latin for ' twin beam', referring to the two rays
forming the spicule. Diagnosis: Didemnid ascidian
spicule having two fusiform rays joined along their shortlengths . The rays share one appendix, inserted between
them at the suture , located towards one pole.
Geminitrabalis depressus sp. nov.
Pl .5, figs 1-6. Derivation of name: From depressus , Latinfor ' low ', or ' pressed down', referring to the way in which
the appendix is inserted between the rays. Diagnosis:
Species of Geminitrabalis having two subrectangularrays, joined along their shorter lengths, and thus forminga marked depression near one pole, along the suture. A
relatively large appendix is inserted in this depression .
Remarks: The width of the spicule rays is equal to , orgreater than , the length of the spicule rays. G. depress us isdistinguished from G. scarabaeus sp. nov. by having a
deep depression and a larger appendix. Moreover, in G.
depressus , the combined width of the rays is greater thantheir length, whereas in G. scarabaeus, the length of theindividual rays is always greater than their combined
width. Holotype : Pl.5 , figs 1, 2 (same specimen).
Dimensions of holotype: Length of ray = 6.0ytm; widthof ray = 3 .OJtm . Type level: Sulaiy Formation(Berriasian) . Type locality: Well MRJN-64, 8563.20 '(core), Marjan Field, offshore eastern Saudi Arabia.
Occurrence: Upper Jurassic-Lower Valanginian .
Geminitrabalis scarabaeus sp. nov.
Pl.5, figs 7, 8. Derivation of name: From scarabaeus,
Latin for a kind of beetle, referring to its resemblance to abeetle. Diagnosis: Species of Geminitrabalis having two
fusiform rays,joined along their length , but forming a relatively small, shallow depression near one pole, along thesuture, in which a relatively small appendix is situated.

45

Remarks: The length of the rays is always greater thantheir combined width. Differs from G. depressus in thelength of the individual rays always being greater thantheir combined width . Holotype: Pl.5, fig.8. Dimensionsof holotype: Length of ray = 7 .Oytm; width of ray =5.5Jtm. Type level: Arab D Formation (Kimmeridgian).
Type locality: Well Qatif-58, 8096.30' (core), Qatif Field,
eastern Saudi Arabia.Occurrence: Upper Jurassic.

Hercolithus gen. nov.
Type species: Hercolithus cricotus sp. nov. Derivation of
name: From herkos , Greek for 'wall', referring to its
wall-like appearance. Diagnosis: Petaloid spicule having
a circular or elliptical wall made up of five to 10 brickshaped rays. The central opening is filled with a variously-shaped process. Remarks: The shape of the rays isvariable. An elongated, pentagonal or square process fills
the central opening. Hercolithus is superficially similar to
genera of the calcareous nannoplankton Family
Polycyclolithaceae, but differs in having a single cycle ofrays/elements. Moreover, these spicules, under XPL withthe gypsum plate inserted, display an opposite colour distribution to genera of the Polycyclolithaceae.
Hercolithus amplexus sp . nov.
Pl.4., figs 23-26. Derivation of name: From amplector,
Latin for 'encircling', referring to the encircling of thecentral process by rays. Diagnosis: An elliptical speciesof Hercolithus made up of five to six rays and an elongated central process. Remarks: A complete specimen was
not photographed. Incomplete specimens photographedhere contain only two or three rays. The complete spicule
has five or six rays. The central process is elongated, but
its shape varies with the ellipticity of specimens.
Holotype: Pl.4, figs 25,26 (same specimen). Dimensionsof holotype: Width of spicule= 5.5ytm; length of spicule= 5.5Jtm (broken). Type level: Sulaiy Formation(Valanginian). Type locality: Well MRJN-64, 8247 .20'
(core), Marjan Field, offshore eastern Saudi Arabia.
Occurrence: Berriasian-Lower Valanginian.
Hercolithus cricotus sp. nov.
Pl.4, figs 20-22. Derivation of name: From erica, Greek
for ' ring ' , referring to the ring-shaped spicule. Diagnosis:
Circular to subcircular petaloid spicule made up of fiveirregularly-sized rays and enclosing a pentagonal central
process. Remarks: The central process is pentagonal inwell-preserved specimens . H. cricotus is distinguishedfrom H. amplexus by being circular and possessing a pentagonal process.lt differs from H. petalus sp. nov. in having fewer rays. Holotype: Pl.4, fig.20 . Dimensions ofholotype: Maximum diameter= 7 .5ytm; diameter of central opening = 2.5ytm. Type level: Arab D Formation(Kimmeridgian). Type locality: Well Qatif-68 , 7221.00'(core), Qatif Field, eastern Saudi Arabia. Occurrence:
Lower Valanginian-Upper Jurassic.

46

Varol

Hercolithus petalus sp. nov.
Pl.4. figs 29 , 34. Derivation of name: From petalon ,Latin for ' leaf', referring to the appearance of the rays .
Diagnosis: Circular to subcircular species of Hercolithus ,comprising eight to 10 irregular, variably-sized rays. The
central opening is filled by a rectangular process .
Remarks: H. petalus is distinguished from H. cricotus inhaving eight to 10 rays , whereas the latter has only fiverays. Holotype: Pl.4 , figs 29 , 34 (same specimen).
Dimensions of holotype: Diameter of spicule= 10.0jtm;
diameter of central opening = 3 .5Jlm. Type level: Arab D
Formation (Kimmeridgian). Type locality: Well Qatif-40,
7481.60' (core), Qatif Field, eastern Saudi Arabia.
Occurrence: Upper Jurassic .
Ommalithus gen . nov.
Type species: Ommalithus clarus sp . nov. Derivation of
name: From omma , Greek for 'eye' , referring to its shape.
Diagnosis: This eye-shaped spicule appears dim (loworder grey) in XPL, unlike other spicules. The central
process is bright in XPL.
Ommalithus clarus sp. nov.
Pl.5 , figs 31-34. Derivation of name: From clarus , Latinfor 'bright', referring to its bright process . Diagnosis:
Relatively small, eye-shaped spicule with a central
process. The ray is dim in XPL (low-order grey) and theappendix/process is bright. Holotype: Pl.5 , figs 31 , 32
(same specimen). Dimensions of holotype: Length =4 .0Jlm ; width = 3.0Jlm. Type level: Sulaiy Formation(Berriasian). Type locality: Well MRJN-64, 8062.70'(core) , Marjan Field, offshore eastern Saudi Arabia.
Occurrence: Berriasian-Lower Valanginian .
Othniodidemnum gen. nov.
Type species: Othniodidemnum arabianicus sp . nov.
Derivation of name: From othneios, Greek for ' strange',referring to the unusual arrangement of the appendices .
Diagnosis: Didemnid ascidian spicule comprising afusiform ray with two appendices, one situated at one poleof the ray, the other unilateral but in proximity to the otherpole. Remarks: Othniodidemnum is distinguished from
Disechinatus in having one of the appendices at its pole.
It is distinguished from Bicephalodidemnum in having
one lateral and one polar appendix. The latter has bipolar
appendices.
Othniodidemnum arabianicus sp . nov.
Pl.3 , figs 20, 25. Derivation of name: After the Arabian
Peninsula, from which it is described. Diagnosis: Spicule
comprising a squarish truncated fusiform ray and bearing
two appendices . The appendices are situated, respectively, at one pole and on one side close to the other pole.
Remarks: 0. arabianicus is distinguished from species of
the genus Disechinatus in having one of the appendicessituated at one pole . It is distinguished from
Bicephalodidemnum amphicarenon in having one lateraland one polar appendix. The latter has bipolar appendices .
Holotype: Pl.3 , figs 20 , 25 (same specimen) . Dimensionsof holotype: Length and width of ray = 5 .OJlm. Typelevel: Sulaiy Formation (Berriasian) . Type locality: Well
MRJN-39, 8200.20' (core), Marjan Field, offshore eastern
Saudi
Arabia .
Occurrence:
Berriasian-Lower
Valanginian.
Paleodidemnum gen . nov.
Type species: Paleodidemnum saudicus sp . nov.
Derivation of name: From paleo , Latin for 'old', referring to the older stratigraphic range of this genus, compared to other didemnid ascidian spicules. Diagnosis:
Spicule having a fusiform , or modified fusiform , ray witha single unilateral appendix. Remarks: Paleodidemnum
is distinguished from Cephalodidemnum by the positionof the appendix; in Paleodidemnum the appendix is single
and unilateral, whereas in Cephalodidemnum, the appendix is polar.
Paleodidemnum acutus sp . nov.
Pl.2 , figs 22, 23 . Derivation of name: From acutus, Latinfor 'pointed', referring to the pointed end of the ray.
Diagnosis: Species of Paleodidemnum having a concavoconvex fusiform ray, which tapers towards one pole. The
single unilateral appendix is located towards the tapered
end of the ray, and situated on the concave side of the ray.
Remarks: P. acutus is distinguished from P. pseudoacutus sp . nov. in the position of its appendix; in the latter
species, this is located away from the tapered end.
Holotype: Pl.2, figs 22, 23 (same specimen). Dimensionsof holotype: Length of ray= 8.5Jlm; maximum width of
ray= 5.0Jlm. Type level: Sulaiy Formation (Berriasian) .
Type locality: Well MRJN-39 , 8225 .70 ' (core), Marjan
Field, offshore eastern Saudi Arabia. Occurrence: Upper
Jurassic-Lower Valanginian.
Paleodidemnum alatus sp. nov.
Pl.2 , figs 34-36. Derivation of name: From alatus , Latinfor 'wing' , referring to the wing-like extension of the ray.
Diagnosis: Species of Paleodidemnum having an elongated fusiform ray with a wing-like extension at one pole. A
relatively large single unilateral appendix is situated in a
relatively broad depression . Holotype: Pl.2, figs 34, 35(same specimen) . Dimensions of holotype: Length of ray= 11.5jtm; maximum width of ray = 5.0Jlm . Type level:
Sulaiy Formation (Berriasian) . Type locality: Well
Marjan-64, 8632.20' (core) , Marjan Field, offshore eastern Saudi Arabia. Occurrence: Berriasian-Lower
Valanginian .
Paleodidemnum caudatus sp. nov.
Pl.2 , figs 12-19; Pl.3 , fig.5 . Derivation of name: From
cauda , Latin for ' appendage ', or ' tail', referring to theposition of the appendix adjacent to the pole of the ray.
Diagnosis: Species of Paleodidemnum having a fusiform
ray with a single unilateral appendix placed adjacent toDidemnid ascidian spicules ...Arabian Peninsula

one of the poles. Remarks: P. caudatus is distinguishedfrom P. saudicus sp. nov. and P. metaxy sp. nov. in having
an appendix adjacent to one pole, whereas in P. saudicus,
the appendix is at the mid-point of the ray, and in P.
metaxy , the appendix lies between the mid-point and poleof the ray. Holotype: Pl.2 , fig .17 . Dimensions of holotype: Length of ray = 6.0Jlm; maximum width of ray =4.0,um . Type level: Arab D Formation (Kimmeridgian).
Type locality: Well Qatif-46 , 7411.40' (core), Marjan
Field, offshore eastern Saudi Arabia. Occurrence: Upper
J urassic-Lower Valanginian.
Paleodidemnum causianus sp . nov.
Pl.3 , figs 3, 4. Derivation of name: From causia , Latinfor 'hat', referring to the location of the appendix.
Diagnosis: Species of Paleodidemnum having a cylindrical fu siform ray with an appendix lying in a relatively
broad depression along one side. Remarks: The base of
the appendix is almost equal in length to the length of theray. P. causianus is distinguished from P. marjanensis sp .
nov. in having a cylindrical ray with a broad depression
along one side, whereas in the latter the ray is trapezoid.
Holotype: Pl.3, figs 3, 4 (same specimen). Dimensions ofholotype: Length of ray= 4 .5Jlm; maximum width of ray= 3.5Jlm. Type level: Sulaiy Formation (Berriasian) . Type
locality: Well Marjan-64, 8237.10 ' (core) , Marjan Field ,offshore eastern Saudi Arabia . Occurrence: Upper
Jurassic-Lower Valanginian.
Paleodidemnum coniger sp. nov.
Pl.3 , figs 21-24. Derivation of name: From coniger,
Latin for 'cone', referring to its conical shape. Diagnosis:
Species of Paleodidemnum having a slightly concavoconvex, rectangular fusiform ray and a conical unilateralappendix . The base of the appendix extends along theentire concave length of the ray. Remarks: P. coniger isdistinguished from P. procerus sp. nov. in having a conical appendix , whereas the latter has a more slender andlarger appendix . Holotype: Pl.3, figs 22, 23 (same specimen). Dimensions of holotype: Length of ray= 5.0Jlm;
maximum width of ray = 2.5Jlm. Type level: SulaiyFormation (Berriasian) . Type locality: Well MRJN-39 ,8231.70' (core) , Marjan Field, offshore eastern Saudi
Arabia. Occurrence: Upper Jurassic-Lower Valanginian.
Paleodidemnum curvus sp. nov.
Pl.3 , figs 6-10. Derivation of name: From curvus , Latinfor ' bent', referring to the bent appearance of the ray.
Diagnosis: Species of Paleodidemnum having a strongly
concavo-convex fusiform ray with a relatively large unilateral appendix . Remarks: P. curvus is distinguishedfrom other species of Paleodidemnum in having a strongly concavo-convex
ray. Holotype: Pl.3 , fig.8.
Dimensions of holotype: Length of ray = 6.5Jlm; maximum width of ray = 2.5Jlm; length of appendix = 6.0Jlm.
Type level: Arab D Formation (Kimmeridgian) . Type
locality: Well Qatif-58 , 7483 .70' (core) , Qatif Field , east-47

em Saudi Arabia. Occurrence: Upper Jurassic-Lower
Valanginian.
Paleodidemnum galbulus sp . nov.
Pl.3, figs 11-15. Derivation of name: From galbulus ,Latin for 'cone of the cypress', referring to its appearance.
Diagnosis: Species of Paleodidemnum having a slightly
concavo-convex modified fusiform ray with a relatively
large appendix attached along almost the entire length of
the flatter side. The suture is straight. Remarks: The
straight suture distinguishes this species from otherspecies of Paleodidemnum . Holotype: Pl.3 , figs 14, 15(same specimen) . Dimensions of holotype: Length of ray= 7 .OJlm; maximum width of ray = 4 .0Jlm; length ofappendix= 4 .5Jlm; maximum width of appendix= 6.0Jlm.
Type level: Sulaiy Formation (Berriasian). Type locality:
Well MRJN-64, 8623.20 ' (core) , Marjan Field, offshore
eastern Saudi Arabia. Occurrence: Upper Jurassic-Lower
Valanginian .
Paleodidemnum marjanensis sp. nov.
Pl.3 , figs 26-30 . Derivation of name: After the Marjan
Field in Saudi Arabia, where this species has been recorded. Diagnosis: Species of Paleodidemnum having a trapezoid fusiform ray, with an appendix located along theshorter length. The appendix lies in a shallow depression ,the base of the appendix being equal to the length of theray. Remarks: The trapezoid ray distinguishes this form
from other species of Paleodidemnum. Holotype: Pl.3 ,fig.30 . Dimensions of holotype: Length of ray= 8.5Jlm;
maximum width of ray = 7 .OJlm. Type level: Arab D
Formation (Kimmeridgian) . Type locality: Well Qatif-48 ,7444.80' (core), Qatif Field , eastern Saudi Arabia.
Occurrence: Upper Jurassic-Lower Valanginian.
Paleodidemnum metaxy sp. nov.
Pl.2 , figs 4-11. Derivation of name: From metaxy, Greek
for ' between ', referring to the position of the appendix
between the positions seen in P. saudicus sp . nov. and P.
caudatus . Diagnosis: Species of Paleodidemnum having
a fusiform ray with an appendix positioned between the
mid-point and one pole of the ray. Remarks: This species
has its appendix mid-way between the mid-point and one
pole. It is thus distinct from P. saudicus sp. nov. (appendix at mid-point of ray) and P. caudatus (appendix adjacent to pole) . Holotype: Pl.2 , fig.6a . Dimensions of holotype: Length of ray = lO.Ojlm; maximum width of ray =4.5Jlm . Type level: Sulaiy Formation (Berriasian) . Type
locality: Well MRJN-64, 8623.20 ' (core) , Marjan Field,
offshore eastern Saudi Arabia. Occurrence: Upper
J urassic-Lower Valanginian .
Paleodidemnum phossonion sp . nov.
Pl.2 , figs 32, 33. Derivation of name: From phosson,
Greek for ' sail' , referring to the appearance of its appendix. Diagnosis: Species of Paleodidemnum having aslightly concavo-convex fusiform ray with a sail-shaped

48

Varol

appendix. The base of the appendix extends along theentire length of the concave side of the ray. Remarks: P.
phossonion is distinguished from P. saudicus sp. nov. andP. procerus sp . nov. in having a sail-shaped appendix .
Holotype: Pl.2, figs 32, 33 (same specimen). Dimensionsof holotype: Length of ray = 7 .Oft m; maximum width of
ray = 3.0ftm; length of appendix = 4.0}lm; width ofappendix = 5.0ftm. Type level: Sulaiy Formation(Berriasian). Type locality: Well MRJN-64, 8546.20 '(core), Marjan Field , offshore eastern Saudi Arabia.
Occurrence: Berriasian-LowerValanginian.
Paleodidemnum procerus sp. nov.
Pl.3, figs 1, 2. Derivation of name: From procerus , Latinfor 'tall ' , or 'slender ', referring to its appendix.
Diagnosis: Species of Paleodidemnum having a relatively small , slightly concavo-convex , rectangular fusiform
ray with a relatively long, slender appendix. The appendix
is attached to the convex side of the ray, its base extending for almost the entire length of the ray. Remarks: The
appendix dominates the species. In P. coniger, the ray isslightly concave where the appendix is attached, unlike inthis species. Holotype: Pl.3 , figs 1, 2 (same specimen) .
Dimensions of holotype: Length of ray= 3.5f!m; widthof ray = 2.5ftm; length of appendix = 6.0ftm. Type level:
Sulaiy Formation (Berriasian). Type locality : Well
MRJN-64, 8557.20' (core) , Marjan Field, offshore eastern
Saudi Arabia. Occurrence: Upper Jurassic-Lower
Valanginian.
Paleodidemnum pseudoacutus sp. nov.
Pl.2, figs 20, 21. Derivation of name: From pseudo,
Greek for 'false' , referring to its false similarity to
Paleodidemnum acutus. Diagnosis: Species of
Paleodidemnum having a ray which tapers towards one
pole. A single unilateral appendix is attached towards theuntapered end of the ray. Remarks: P. pseudoacutus isdistinguished from P. acutus in the position of the appendix. Holotype: Pl.2 , figs 20, 21 (same specimen).
Dimensions of holotype: Length of ray = 8.5f!m; maximum width of ray= 5.0ftm. Type level: Sulaiy Formation(Berriasian) . Type locality: Well MRJN-39 , 8225.70'(core) , Marjan Field, offshore eastern Saudi Arabia.
Occurrence: Upper Jurassic-Lower Valanginian.
Paleodidemnum saudicus sp. nov.
Pl.2 , figs 24-31.
1971 Didemnoides minutum Bonet & BenvenisteVelasquez, pp.l0-11, pl.l, figs 8, 10, 17, 18; nonpl.l , figs 1-7 , 9, 11-16, 19.
1994 Didemnoides minutum Bonet & BenvenisteVelasquez: Varol & Girgis, Fig .10(20).
Derivation of name: After Saudi Arabia , from where thisspecies is described. Diagnosis: Species of
Paleodidemnum having a fusiform ray with a single unilateral appendix at its mid-point. Remarks: P. saudicus isdistinguished from P. caudatus and P. metaxy in having anappendix at the mid-point of the ray. This is adjacent to
one pole in P. caudatus and between the mid-point andone pole in P. metaxy. Holotype: Pl.2, figs 27, 28 (samespecimen) . Dimensions of holotype: Length of ray =8.5ftm; maximum width of ray = 3.5f!m. Type level:
Sulaiy Formation (Berriasian). Type locality: Well
MRJN-64 , 8515.20 ' (core), Marjan Field, offshore eastern
Saudi Arabia . Occurrence: Upper Jurassic-Lower
Valanginian.
Unabaculus gen. nov.
Type species: Unabaculus pseudobscurus sp. nov.
Derivation of name: From unio , Latin for 'jointed' , andbaculus , Latin for ' rod ' , referring to its two joined rays.
Diagnosis: Spicule made up of subtrapezoid duplex
fusiform rays, joined along the short length of the subtrapezoid , with bipolar appendices located in depressions
formed at the poles of the joined rays. Remarks:
Unabaculus is distinguished from Didemnobijugatus byhaving appendices.
Unabaculus pseudobscurus sp. nov.
Pl.4, figs 5-11. Derivation of name: From pseudo, Latinfor 'false', referring to its superficial similarity to thecalcareous nannofossil Calculites obscurus . Diagnosis: The
spicule is made up of subtrapezoid duplex fusiform rays,
joined along their short lengths . Two bipolar appendices
sit in the depressions formed at the ends of the suture
between the rays. Remarks: This form differs from thenannofossil species Calculites obscurus by lacking a rim .
The latter is also flatter and larger. Holotype: Pl.4, figs 7,
8 (same specimen). Dimensions of holotype: Length of
spicule = 6.0ftm ; width of spicule = 5.0ftm. Type level:
Sulaiy Formation (Berriasian). Type locality: Well
Marjan-64, 8538.70 ' (core) , Marjan Field, offshore eastem Saudi Arabia. Occurrence: Upper Jurassic-Lower
Ryazanian .
Velasquezia gen . nov.
Type species: Velasquezia praegothica (Herrle) nov.
comb. Derivation of name: In honour of N. BenvenisteVelasquez (Institute Mexicano Del Petroleo, Mexico),didernnid ascidian specialist. Diagnosis: Spicules madeup of four joined fusiform rays. Remarks: The joined partof the rays is usually shorter than the free part of the rays .
The rays are identical in size in well-preserved specimens.
Velasquezia differs from Acinodidemnum in having fourrays, whereas the latter has a single ray and two bilateralappendices . Velasquezia is superficially similar in appearance to species of the calcareous nannofossil genus
Uniplanarius but differs in having a single cycle. Speciesof Velasquezia, in XPL with a gypsum plate inserted, display an opposite colour distribution to that of species ofUniplanarius.
Velasquezia minuta (Bonet & Benveniste-Velasquez)comb. nov.

Didemnid ascidian spicules ... Arabian Peninsula

Pl.l, fig.29. Basionym: Didemnoides minutum Bonet &Beneviste-Velasquez, 1971 , pp .11-13, pl.l , figs 3, 4 , 7,
11; non pl.l , figs 1, 2, 5, 6, 8-10, 12-19. Revista delInstituto Mexicano del Petroleo, 3: 8-35 . Remarks: In
this spicule, four fusiform rays are joined to form anasymmetrical cross. The opposite angles of the cross areequal. The free parts of the rays are usually longer than
the joined lengths. Occurrence: Upper JurassicPleistocene.
Velasquezia praegothica (Herrle) comb. nov.
Pl.l, figs 21-24. Basionym: Uniplanarius praegothica
Herrle, 2002, p.78 , pl.6, fig.23 . Institut und Museumfiir
Geologie und Paliiontologie der Universitiit Tubingen,
27: 1-114.
1971 Didemnoides minutum Bonet & BenvenisteVelasquez , pp.l1-13 , pl.l , figs 9, 12; non pl.l, figs
1-8, 10, 11 , 13-19.
Remarks: The spicule is made up of four fusiform rays .
The spicule rays are joined to each other at right-angles.
V praegothica is distinguished from V minuta by thearrangement of the rays . In V. praegothica , the rays joineach other at right-angles to form a symmetrical cross ,whilst in V. minuta, the rays make an asymmetrical cross,in which opposite angles are equal. Occurrence: Upper
J urassic-Pleistocene .

4.2 Calcareous nannofossils
Cyclagelosphaera Noel , 1965
Cyclagelosphaera riyadhensis sp. nov.
Pl.2 , figs 1-3 . Derivation of name: After Riyadh, capitalof Saudi Arabia, from where this form has been recorded .
Diagnosis: A large species of Cyclagelosphaera (1013ptm) with 24 to 36 elements in the distal shield.
Remarks: This species of Cyclagelosphaera is relatively
large, with a small, closed central-area, enclosed by a narrow tube-cycle . The placolith shields are monocyclic andbirefringent in XPL. C. riyadhensis is distinguished from
Cyclagelosphaera deflandrei by its smaller size. The latter has a minimum size >13ptm and is not recorded above
the Lower Oxfordian Hanifa Formation in the Arabian
Peninsula. Poorly-preserved specimens of C. riyadhensis
may be confused with the ascidian spicule Didemnoides
radiatus, however, C. riyadhensis always appears brownish to yellowish in XPL, whereas D . radiatus appears
brownish-blue. Moreover, C. riyadhensis has distinct
black gyres/extinction lines , a defined central-area and a
tube-cycle, whereas D . radiatus lacks these features.
Holotype: Pl .2, fig .1. Dimensions of holotype: Diameter
12 .0ytm . Typelevel: Jubaila
Formation(Kimmeridgian). Type locality : Diplomat outcrop ,Sample D-68 , near Riyadh , Riyadh-Mecca highway, central Saudi Arabia. Occurrence: Upper Jurassic . The last
occurrence of this form was noted at the top of the Jubaila
Formation.

49

Acknowledgements
I would like to thank Saudi Aramco and the Ministry ofPetroleum and Mineral Resources of Saudi Arabia for permission to publish this paper. The editorial assistance and lithostratigraphic advice of Dr. Wyn ap Gwilym Hughes , of Saudi
Aramco's Geological Technical Services Division , is gratefully
acknowledged. Thanks also to Dr. Giuliana Villa for checking
the Latin names. I would especially thank to Dr. Jackie Lees forher meticulous review of the manuscript.

References
Bonet , F. & Benveniste-Velasquez , N. 1971. Espiculas deascidias fosiles y actuales. Revista del lnstituto Mexicanodel Petroleo , 3: 8-35.
Bown,
P.R . (Ed.).
1998.
Calcareous Nannofossil
Biostratigraphy. Kluwer Academic Press , London: 315pp.
Bown , P.R. & Young , J.R . 1988 . Techniques. In: P.R. Bown
(Ed .). Calcareous Nannofossil Biostratigraphy. Kluwer
Acedemic Press , London: 86-131.
Clarke , M.W.H. 1988. Stratigraphy and rock unit nomencl aturein the oil-producing area of interior Oman. Journal of
Petroleum Geology, 11(1 ): 5-60.
Cooper, G.A. 1987. Jurass ic brachiopods of Saudi Arabia.
Smithsonian Contributions to Paleobiology, 65: 1-213 .
Deflandre , G. & Deflandre-Rigaud , M. 1956. Micrascidites
manip. nov. , sclerites de Didemnides (Ascidites, Tuniciers)
fossiles du Lutetian du Bassin Parisien et du Balcombien
d' Australia. Compte Rendus Sommaire de la Societe
Geologique de France , 4: 47-48.
Enay, R. 1987. Le Jurassique d ' Arabie Saoudite Centrale.
Geobios, Memoire Speciale, 9: 1-316 .
Herrle , J.O. 2002. Paleoceanographic and paleoclimatic implications of mid-Cretaceous black shale formation in the
Vocontian Basin and the Atlantic: Evidence from calcareous
nannofossils and stable isotopes. lnstitut und Museum fiir
Geologie und Paliiontologie der Universitiit Tubingen, 27:
1-114.
Hughes , G.W. 2004 . Middle to Upper Jurassic Saudi Arabiancarbonatepetroleumreservoirs:biostratigraphy,
micropalaeontology and palaeoenvironments. GeoArabia,
9(3): 79-113.
Hughes , G.W., Dhubeeb , A.G. , Varol, 0. , Lindsay, R . & Mueller,
H. 2004. The Arab-D biofac ies of Saudi Arabia - theirpalaeoenvironment and new biozonation. GeoArabia , 9( 1):79-80.
Jafar, S.A . 1983. Significance of late Triassic calcareous nannoplankton from Austria and so uthern Germany. Neues
Jahrbuch fiir Geologie und Paliiontologie Abhandlungen,
166: 218-259.
Manivit, H. 1987 . Distribution des nannofossiles calcaires duJurassique moyen et superieur en Arabia Saoudite
centra1e.Geobios Memoire Speciale , 9: 277-291.
Noel , D . 1956. Coccolithes des terrains Jurassiques de I' Algerie.
Publications du Service de la Carte Geologique de l 'Algerie(Nouve lle Serie), Traveaux Collaborateurs, 8: 303-345.
Noel , D. 1965. Sur Jes coccolithes du Jurassique Europeen , etd ' Afrique du Nord. Editions du Centre National de laRecherche Scientifique, Paris: 299pp.
Perch-Nielsen, K . 1988 . New Lower Cretaceous nannofossil
species from England . International Nannoplankton
Association Newsletter, 10: 30-36.
Sharland, P.R ., Archer, R ., Casey, D.M ., Davies, R.B. , Hall ,S.H. , Heward , A.P. , Horbury, A .D. & Simmons , M .D. 2001.

50

Varol

Arabian plate sequence stratigraphy. GeoArabia, Special
Publication, 2: 1-371.
Varol, 0 . & Girgis , M.H. 1994. New taxa and taxonomy of someJurassic to Cretaceous calcareous nannofossils. Neues
Jahrbuch for Geologie und Paldontologie Abhandlungen,192: 221-253.
Varol, 0. & Houghton , S. 1996. A review and classification offossil didemnid ascidian spicules . Journal of
Micropalaeontology, 15: 135-149.

Didemnid ascidian spicules ... Arabian Peninsula

51

Plate 1

Fusellinus inso/itus(MRJN-39, 8169.2')

Fusellinus inso!itus(MRJN-39, 8169.2 ')Didemnorribaculus anceps D . anceps(HRDH-87, 7074.1 ')(HRDH-87 , 7074. 1')

D. anceps(MRJN-39, 8 169.4 ')'·~.••\;'·_.·. .
.

-;.

-..:

Fusellinus brevis(MRJN-39, 8 103.7')

F. brevis(MRJN-39, 8103. 7')

-

'

.•

F. brevis(Qatif-67 , 7 124.5')

Fusellinus elongatus(Qatif-58, 7438. 7')

F. e/ongatus(Qatif-58, 7438 .7')

A. lineola

A. ecpalesis(MRJN-64, 8107')@

Acinodidemnum linea/a(Qatif-48 , 7946' )A.lineo/a(MRJN-64, 7407')

A.lineola(HRDH-87, 7074. 1' )Velasquezia praegorhica(MRJN-64, 8240.2 ')V. p raegothica(MRJN-64, 8240.2')

Velasquezia praegorhica(LWHH-17,8 191.2 ')Acinodidemnum arcuatus(MRJN-39, 7981.2 ')(HRDH-87, 7074. 1')

A. ecpalesis(LWHH- 17, 8656.2 ')A. arcuatus

V minuta(LWHH-17, 7996.7')(LWHH- 17,8 191.2 ')A. ecpalesis(LWHH-1 7, 8656.2')

Varol

52

Plate 2
Cyc/age/osphaera, Paleodidemnum

Cy clage/osphaera riyadhensis C. ri )'adhensis(Diplomat, D-68)(Dipiomat, D-68)

P. metaxy(LWHH-2, 7906.35 ')C. riyadhensis(Diplomat, D-68)

Pa/eodidemmtm metCL\)' P. meraxy(LWHH-17, 8258.7')(MRJN-64, 8623.2')

Paleodidemnum meran,(LWHH-2, 8074. 3' ) .

P. m e ttL\).
(LWHH-2 , 8074.3')

P. metaxy(Qatif-58, 746 1')

Paleodidemnum caudatus P. caudatus(LWHH-1 7, 8206.2 ')(LWHH-17 , 8206.2')

P. metal)'(Qatif-58, 7442.9')

P. caudatus(Qatif-58, 7446.8 ')P. caudatus(Qatif-58, 7465 ' )Paleodidemnum caudatus Paleodidemnum caudarus(Qatif-46 , 7411.4 ')(LWHH-1 7, 8152.2')

P. meta..ty(Qatif-58, 7442 .9')

P. caudarus(Qatif-58, 7465 ' )Paleodidemnum pseudoacutus(MRJN-39, 8225.7')

Paleodidenmum acwus(MRJN-39, 8225.7')

Paleodidemnum saudicus(LWHH-17, 8152.2 ')Paleodidemnum saudicus(MRJN-64, 8515.2')

P. saudicus(Qatif-40, 7502 ' )P. saudicus(Qatif-58, 2476.8')~

Pa/eodidemnum phoS.!t.'Piui"

Pa/eodidemnum alar us

P. a latus(MRJN-64, 8546.2 ' )(MRJN-64, 8632.2 ' )(M RJ N-64, 8632.2 ')lO}tm

Didemnid ascidian spicules ...Arabian Peninsula

53

Plate 3._,••

Paleodidemnum 1 Diplinthos 1 Othniodidemnum 1 Didemnoides~-

Holot~· pc

1

Paleodidemnum procerus(MRJN-64, 8557.2 ' )'J.·.·f,

Holotype

Paleodidemnum causianus(MRJN-64, 8237. 1')

P. caudatus(LWHH- 17, 8 152.2 ' )

I

1

••
'

Paleodidemnum curvus(MRJN-64, 8 179.2')

P. curvus(MRJN-64, 8 179.2')

P. curvus(Qatif-58, 7483.7')

Paleodidemnum curvus(Qatif-40, 7502')1, .

llol otypc

1'.

~~

Paleodidemnum galbulus P. ga!bulus(Qatif-40, 7548.3 ')(MRJN-39, 7992.2 ')P. galbu lus(MRJN-39, 8097.7')

Diplinthos qatijensis(Qatif-40, 7485.8 ')Dip!inthos qatifensis(Qatif-40, 7485.8 ')Pa!eodidemnum ga!bu!us(Qatif-48, 7444. 8')

0. arabianicus(MRJN-39, 8200.2 ')

.,.,.
1..

ll olotyporPaleodidemnum coniger(MRJN-39, 8046. 1')

Paleodidemnum coniger(MRJN-39, 823 1. 7')

Paleodidemnum marjanensis(MRJN-39, 8073.7')

Didemnoides radiarus(Wadi Laban, 40')\

P. marjanensis(Qatif-48, 7444.8')

Didemnoides radiatus(Wadi Laban, 40')

P. coniger(MRJN-39, 8046. 1')

0. arabianicus(MRJN-39, 8200.2')

P. marjanensis(MRJN-39, 8072.7')

P. marjanensis(Qatif-48, 7444. 8' )Didemnoides rosetta(Diplomat, D-11 9)lOJim

Didemnoides roserra(Qatif.-49, 7439.2')

Varol54

Plate 4B. delicatus(LWHH-17, 8511.2 ' )Bactrolithus delicarus(Qatif-48, 7496')

B. delicatus(MRJN-39, 8366.7')....·-~

B. delicatus(LWHH-17, 8511.2')--•

Unabaculus pseudobscurus(MRJN-64, 8538.7')

U pseudobscurus(LWHH- 17, 8397.2')

Cephalodidemnwn pseudocarenon(MRJN-64, 8225.2' )C. pseudocarenon(MRJN-64, 8 15 1.2' )Bicephalodidemnum amphicarenon

Cephalodidemnum carenon

C. pseudocarenon(MRJN-39, 8372. 7')(MRJN-39, 8269.2 ')(MRJN-64, 8225 .2')

Unabaculus pseudobscurus(MRJN-39, 8261.7')

Unabaculus pseudobscurus(MRJN-64, 8225.2 ' )

•

Q

~'

Hercolithus cricotus

Hercolithus cricotus(Qatif-68, 7221 ' )(MRJN-64, 8030.2')

Hercolithus amplexus(MRJN-64, 8247.2 ' )Didemnobijugatus dichotomus(LWHH-17, 8683.2')

~~

e..

llolotyrc

Hercolithus amplexus(LWHH-1 7, 8058.7')'
Didemnobijugatus zigzag(MRJN-64, 85 11.2')

Hercolithus petalus(Qatif-40, 7481.6' )Didemnobijugarus dichotomus(LWHH- 17, 8683.2')

Hercolithus petalus(Qatif-40 , 748 1.6')

lOp m

ss

Didemnid ascidian spicules ...Arabian Peninsula

Plate 5
Geminitrabalis, Disechinatus, Ommalithus

Geminitrabalis depressus(MRJN-64, 8563.2 ' )•G. depressus(MRJN-64, 8030.2' )G. depressus(MRJN-39, 8073.7')

G. scarabaeus(Qatif-58, 8096.3')(Qatif-48 , 7598.3 ' )G. depress us(MRJN-39, 8073. 7')i, . ....... l•'4l'r .•. .

Geminitrabalisdepressus G. scarabaeus(MRJN-39, 8081.2')(MRJN-64, 8308.2')

Disechinatus se/en ion

,
•.
··~
•
-

- 1

i

Disechinatus clausus(MRJN-39, 81 11.2' )D. clausus(Qatif-58 , 7475')

Disechinatus baculus

D. clausus(Qatif-58, 7475')

D. clausus(MRJN-39, 8 11 1.2')

D. baculus(Qatif-46, 744 1.2')(Qatif-46, 7441.2 ' )•(MRJN-64, 8092.5')•..

D. selenion(MRJN-64, 8255.4')

Disechinatus baculus··· ···~""
Disechinaws carinatus(Qatif-58 , 8091.2')

D. carinatus(Qatif-64, 7946.7')

D. carinatus

Disechinatus mediageminus(Qatif-64, 7946.7')(MRJN-64, 8600 .7')

D. bicaudatus(MRJN-64, 8323 .2')

D. bicaudatus(MRJN-64, 8372.2')

Holotyp'~~~ .
:ifl',
Disechinatus bicaudatus(MRJN-64, 8364.7')

Ommalithus clarus(MRJN-64, 8062 .7')

D. bicaudatus(MRJN-64, 8323.2')

Ommalithus clarus(MRJN-64, 8 144.7')to,,m

D. mediageminus(MRJN-64, 83 19.2 ' )Gen. et sp. indet.
(MRJN-64, 8364 .7')